Year	Percent
1979	3.43113
1980	2.75527
1981	2.73441
1982	2.34951
1983	2.54588
1984	2.40795
1985	2.19286
1986	2.04004
1987	1.98119
1988	2.11178
1989	2.0277
1990	2.06851
1991	1.95811
1992	1.82857
1993	2.11206
1994	1.70576
1995	1.65869
1996	1.57503
1997	1.51536
1998	1.49259
1999	1.52195
2000	1.33263
2001	1.4124
2002	1.39414
2003	1.41212
2004	1.33917
2005	1.42878
2006	1.58735
2007	1.70859
2008	1.62008
2009	1.67661
2010	1.51351
2011	1.60139
2012	1.38221
2013	1.58335
2014	1.53207
2015	1.57846
2016	2.08079
2017	1.89663